Method and apparatus for preventing erosion

ABSTRACT

This invention relates to a method and apparatus for preventing erosion of beaches by tidal waves, comprising placing hollow enclosures, such as &#39;&#39;&#39;&#39;quonset&#39;&#39;&#39;&#39; type huts, end-to-end along the beach, with slots on the walls of the huts, and wherein the huts are so placed that incoming tidal waves will be diverted over the roofs of the huts. Incoming and outgoing waves will be retarded in velocity by flowing through said slots and sand will be deposited and accumulated inside the huts. Reduction of wave velocity will cause deposition of sand particles as waves ride over the hut. Additionally, slots in the hut will cause incoming and outgoing waves to become retarded in velocity by flowing through said slits and sand will be deposited and accumulated inside the huts.

United States Patent Stickler, Jr. [45] Apr. 4, 197 2 54] METHOD AND APPARATUS FOR 877,057 9/1961 Great Britain ..61/4

PREVENTING EROSION Primary Examiner-Jacob Shapiro [72] Inventor: Charles W. Stlckler, Jr., Mohnton, Pa. Atmmey wmiam Ruano [73] Assignee: Gray Tech Industries, Inc.. Mohnton, Pa.

4 [57] ABSTRACT [22] Filed: Apr. 9, 1970 This invention relates to a method and apparatus for prevent [21] Appl' 26829 ing erosion of beaches by tidal waves, comprising placing hollow enclosures, such as quonset" type huts, end-to-cnd along 52 us. c1 ..6l/4, 61/11 the beach, with slots on the walls of the huts, and wherein the [51 Int. Cl ,,E02b 3/04 huts are so placed that incoming tidal waves will be diverted [58] Field of Search "61/3, 4, 2, 46, 37, 11 over the roofs of the huts. Incoming and outgoing waves will be retarded in velocity by flowing through said slots and sand [56] References Cited will be deposited and accumulated inside the huts. Reduction of wave velocity will cause deposition of sand particles as UNITED STATES PATENTS waves ride over the hut. Additionally, slots in the but will 2,069,715 2/1937 Arpin ..61/4 cause incoming and Outgoing waves to become retarded in 421,631 2/1890 Sutherland velocity y flowing through Said slits and Sand will be 2.474 786 6/1949 Humphrey deposited n accumulated in i the h 7 1.17596. 3/1916 Latham 2 Claims 2 Drawing Figures FOREIGN PATENTS 0R APPLICATIONS 1,019,527 10/1952 France ..61/3

PATENTED PR 4 I972 LAND SIDE SEASIDE INVENTOR CHARLES W. STICKLERJR.

his ATTORNEY METHOD AND APPARATUS FOR PREVENTING EROSION This invention relates to a method and apparatus for preventing or minimizing erosion of beaches by tidal waves.

The sea is busily eating up great chunks of US. coastline, costing land and home owners millions of dollars a year.

In Florida alone, a survey showed today, annual losses have been running at a rate of $10.6 million.

Excluding Florida, a recent federal study estimated erosion damage along the Gulf and Atlantic coasts from Texas to New England at $31 million annually.

Waves and storms have washed out 3,000 acres of oyster beds and beach along Willapa Bay on the Pacific coast of Washington.

Virginia Beach, a Virginia resort area, pumps sand hours daily during the off-season to replace what is lost to the encroaching waters.

The Montauk Point lighthouse on the southern tip of Long Island, whose beacon has guided mariners since 1797, stands on a clifi which has been eroded almost away.

In Cape May, N.J., two convents, two lighthouses, a Coast Guard radar station and nearly a fourth of the communitys land area have been claimed by the Atlantic Ocean.

The chief factors in marine erosion are mechanical and are caused by the attack of waves upon the land in the form of hydraulic action, abrasion, and transportation.

Forces of hydraulic action by the impact of large waves of surging water have been measured by a dynamometer on the coast of Scotland and show an average of 611 pounds per square foot in summer to 2,086 pounds per square foot (extremes up to 6,083 pounds) in winter. This force when thrust against a land mass has great destructive power. The force of impact also compresses air in the internal land mass causing additional hydraulic splitting away ofland mass.

Abrasive action generated by sand and gravel rubbing against the land in the wave onslaught is the greatest erosive force. In great storms, particle size can include boulders or other debris in motion. The back and forth movements in the waves gradually cause the rounded small fragments of sand.

If it were not for the transport of the particles of rock debris by backwash, undertow, tidal currents, and longshore currents, a gradual build-up of protective quantities of sand would occur. The sand removal by these transport elements, therefore, must be combatted mechanically if a deposit of sand is to be obtained rather than its removal back to the sea.

The circular motion of the water in an unbroken wave causes a grain of sand on the shallow sea bottom to be lifted up and carried slightly forward as each wave crest passes and then carried down and back to its original position by the trough of the wave, so that no actual transport of the sand particle is accomplished by the wave itself. However, when the particle is lifted free of the bottom, gentle currents can cause movement of the particles which the wave itself will not transport.

As waves reach shallow water and begin to drag on the bottom, the movement ceases to be one of oscillation as the water rolls ahead and drags sediment with it. Since the waves drag bottom only when approaching the shore, they have a tendency to move the particles toward the land.

Opposing the particle movement landward by wave and current is the major undertow force which tends to shift the particles down the seaward slope. The net movement is almost continuous seaward motion of the particles to places too deep to be affected by motion of the water.

If sediment is so abundant that undertow or longshore currents cannot overcome deposition, then there is the tendency to have a build-up of particles into a protective beach. Not-soabundant particle sediment may possibly provide deposition if undertow or longshore currents can be minimized by relieving those currents of their carry-back velocity. Thus, if the incoming wave can be permitted to ride over a designed beach break-water and the resultant return flow is impeded sufficiently to reduce its velocity, then particles will be deposited.

The gradual deposition of these particles will then build up to a protective beach deposit.

It is proposed, by the present invention, that elongated semi-cylinders (quonset shaped) having floor and partial end closure be placed in pre-determined, chain-like relationship, one-to-the-other, so as to accept the free ride of either direct or longshore waves. This alignment is to be determined by the immediate local conditions of historical wave pattern. The structures are to be constructed of concrete with slotted areas to relieve water pressure in the seaward return of the wave. Deposition of sand occurring in the area behind the structure and internally as the water swishes through the longitudinal slots of the structure, stabilize both the structure and the shore erosion areas. Gradually the unit is covered by deposited sand and provides a satisfying stabilized protective barrier against erosion.

Anchoring of the quonset but like structures against unusual forces may be accomplished by drag footers cast in the structure. Further, anchoring may be obtained by placement of vertical concrete piles at the forward comers of each structure. Piles will also baffle water return forces between structures. Separation of the structures is designed to relieve some backflow water pressure and pile baffles will help maintain a reduced water velocity. In those areas of coast subject to severe seasonal wave action, the locking together of the quonset hut-like structure to these pile bafi'les may be advisable.

Pile baffles of concrete, reinforced with metal rods or wire mesh, may be constructed utilizing auger drills of calculated diameter, galvanized metal liners, and on-site poured concrete.

Chemical soil solidification may be used for further stability of the structures as may be determined for each erosion problem.

Coastal erosion problems, such as that at Miami Beach, may be provided with some control by off-shore placement of the quonset hut structures to trap-out sand particles. The below water placement will permit change in the incoming current velocities and the attendent undertow currents to establish new sand deposition. Location of the placement would be based on the history of the individual coastal areas.

An object of the present invention, therefore, is to provide elongated hollow structures, such as quonset huts, abutted end-to-end, without intermediate walls and having slots in the walls seaside as well as landside through which tidal waves may pass and deposit sand particles in the huts.

Another specific object of the invention is to provide said huts with comparatively deep anti-scouring footers, both seaside and landside, to prevent development of erosion paths underneath the structure, particularly from the shore side to the seaside by water return under the flat bottom slab forming the floor of the quonset hut.

Other objects and advantages will become more apparent from a study of the following description taken with the accompanying drawing wherein:

FIG. 1 is a perspective view of a structure embodying quonset hut-like enclosures, arranged end-to-end along a beach or coastline to prevent or minimize erosion of the coast by tidal waves; and,

FIG. 2 is an end view of the structure shown in FIG. 1.

Referring more particularly to FIGS. 1 and 2 of the drawing, numeral 1 denotes quonset hut structures arranged end-to-end wherein the end walls of the abutting ends may be omitted if so desired. If desired, the ends may be interfitted and grouted together to form a continuous wall. Numeral 2 denotes a substantially semi-circular wall preferably of cementitious material, such as concrete, or plastic material which may be cast by having an outer rigid form and an inner expansible form, such as a tubular form, which may be expanded by introducing air therein such as described in my pending Pat. application, Ser. No. 16,109 filed Mar. 2, 1970, entitled PORTABLE MOLD AND METHOD FOR ERECTING CONCRETE OR PLASTIC SI-IELTERS.

Since numerous tests indicate that the greatest concentration of pressure, by the tidal wave as it strikes the seaside portion of the structure, is at the base portion 4, it is desired to provide such base portion 4 with a reverse or concave curvature, as shown, so as to assist or divert the wave in an upward direction so that it will flow over the roof of the huts 1 as the wave moves toward shore. In so moving, part of the wave will infiltrate the slots 7 and pass through the hollow portion of huts l and by virtue of the reduction of velocity of the waves, sand particles will drop off and will be deposited on the cement slab 5 forming the floor of the huts.

As the waves move from landside to seaside, a substantial portion will flow through slots 7 on the landside and will be retarded in velocity enough to deposit more sand on the floor 5. Thus with each movement of the tidal waves, sand will be deposited in the huts and will eventually fill them.

A relatively deep footer 6 is provided seaside to prevent high pressures of the wave from eroding a path under the surface of the floor slab 5. The greatest erosion tendency underneath the floor slab occurs when the waves move from the shore toward the sea, and for this reason a footer 8 is provided there having at least the same depth and preferably a larger depth than footer 6 so as to block the flow of water underneath the floor as the wave recedes from the shore towards the sea.

Test data have been recorded involving about 200 observations of wave heights and periods and their effects on the above-described structure.

Average pressures were recorded at about approximately 200 pounds per square foot against simulated smaller structures. Maximum shock pressures of 1,000 pounds per square foot of 1/10 second duration have been observed, occasionally, such as with a 5-foot wave of a 3-second period against an equivalent S-foot radius structure. It was observed that continuous non-breaking waves cause high shock pressures. As the waves are thrust radially of the structure, seaside maximum pressures are concentrated in the lower front area of the arc or curved base portion 4 through substantially an angle of 30. The pressures then progressively decrease in intensity above the 30 area, as indicated by the arrows, and on the backside or landside of the structure, a negative pressure develops (tensile stress). These pressure points or varying forces indicate that the thickness in strength should be greatest at base portion 4, the reverse radius of which enables acceptance of the wave forces and diversion or deflection thereof in an upward direction to facilitate movement of the wave over the roof of the structure.

The front or seaside anti-scouring footer 6 may be of the order of 2 feet in depth, or possible more, particularly where the coast has a greater angle of taper. However, the landside anti-scouring footer 8 should be at least the same (unless taper of the land does not require it) or greater in depth than the seaside footer 6.

Anti-scouring footers 6 and 8 serve as drag" footers designed to brake any movement of the waves underneath the floor slab which would tend to erode the ground underneath slab 6.

While oniy one row of slots 7 are shown landside and seaside, obviously several rows, preferably with the slots offset or staggered, may be used instead.

In some applications, either the landside slots or the seaside slots may be omitted.

While I have illustrated the hut structures 1 as being above the surface of the beach and of the normal water level, they maybe, instead, completely submerged under the normal water adjacent the beach to prevent or minimize erosion.

Thus it will be seen that l have provided an efficient method and apparatus of preventing or minimizing abundantly costly erosion of beaches by a hollow slotted structure arrange along the coast substantially at right angles to the direction of the tidal waves.

While I have illustrated and described several embodiments of my invention, it will be understood that these are b way of illustratlon only and that various changes and modt ications may be made within the scope of the following claims.

I claim:

1. The method of minimizing erosion of a beach by tidal waves comprising, extending a perforated, substantially semicylindrical wall, having a concave outer base section, along a substantial length of the beach, generally at right angles to the direction of the waves, and positioning said concave base portion immediately above the surface of said beach, facing said body of water, so that said wall and concave base portion will deflect a portion of the oncoming tidal waves over said wall while the perforations will pass a portion of said waves laterally trough said hollow unobstructed wall to entrap sand particles within said wall and slow down the velocity of said waves.

2. A structure for minimizing erosion of a beach from tidal waves from a body of water, comprising an unobstructed hollow enclosure defined by a cementitious, substantially semicircular; wall supported on a cementitious horizontal floor, said floor having outer end portions projecting beyond the outer radius of said wall, spaced parallel footers extending downwardly, substantially at right angles to said floor and end portions and below the beach surface to prevent flow of water and scouring underneath said structure, said structure extending along a substantial length of the coast of said beach, the base portion of said wall adapted to face said body of water being concavely curved so as to deflect tidal waves over the top of said structure, said wall having slots along the sides thereof through which said waves may pass laterally through said unobstructed enclosure to reduce their velocity and deposit sand particles carried thereby into said enclosure and on said floor. 

1. The method of minimizing erosion of a beach by tidal waves comprising, extending a perforated, substantially semicylindrical wall, having a concave outer base section, along a substantial length of the beach, generally at right angles to the direction of the waves, and positioning said concave base portion immediately above the surface of said beach, facing said body of water, so that said wall and concave base portion will deflect a portion of the oncoming tidal waves over said wall while the perforations will pass a portion of said waves laterally trough said hollow unobstructed wall to entrap sand particles within said wall and slow down the velocity of said waves.
 2. A structure for minimizing erosion of a beach from tidal waves from a body of water, comprising an unobstructed hollow enclosure defined by a cementitious, substantially semi-circular; wall supported on a cementitious horizontal floor, said floor having outer end portions projecting beyond the outer radius of said wall, spaced parallel footers extending downwardly, substantially at right angles to said floor and end portions and below the beach surface to prevent flow of water and scouring underneath said structure, said structure extending along a substantial length of the coast of said beach, the base portion of said wall adapted to face said body of water being concavely curved so as to deflect tidal waves over the top of said structure, said wall having slots along the sides thereof through which said waves may pass laterally through said unobstructed enclosure to reduce their velocity and deposit sand particles carried thereby into said enclosure and on said floor. 